ABSTRACT Support is requested for a Keystone Symposia meeting entitled Molecular Mechanisms of Heart Development, organized by Drs. Benoit G. Bruneau, Brian L. Black and Margaret E. Buckingham. The meeting will be held in Keystone, Colorado from March 26-30, 2017. The heart is the first organ to form in the embryo, and its development and function is essential for life. Defects in heart formation result in congenital heart disease, which affects at least 1% of live births. The lessons learned from heart development are also critical for the development of strategies aimed at regenerating diseased adult hearts. This meeting will address advances in our understanding of cellular and molecular mechanisms of heart development, with a view toward congenital heart disease and cardiac regeneration. Developmental biologists, cardiologists, geneticists and basic scientists from many disciplines can discuss current findings and promote multi-disciplinary collaborations. Opportunities for interdisciplinary interactions will be significantly enhanced by the concurrent meeting on RNA- Based Approaches in Cardiovascular Disease, which will share a keynote address and two plenary sessions with this meeting. NHLBI Relevance: NHLBI, through its many programs, supports research towards understanding heart disease. In particular, the NHLBI?s Bench to Bassinet program is focused on understanding heart development and congenital heart disease, the topic of this conference.